Doing an Ancestry DNA test is probably the best thing I have done in the last year.
My Gran was brought up in an orphanage and she never really knew her parents. Finding information on her father was quite easy, but her mother proved a problem. Her name was Florence May Bannister, I had her wedding certificate which showed her father as Henry but I had no other information, including where she was from or her exact age (although I did know she celebrated her birthday on the 5th April). I narrowed my search down to one birth record, that of Florence Bannister born on the 31st March 1887 but I was not 100% certain I was looking at the same person as both the birth date was wrong and the lack of a middle name. The very first hit I had on Ancestry through the DNA was from a great nephew of the Florence Bannister born on the 31st March 1887, I now know for certain that I was looking at the correct ancestor! (And for the record my Gran was right with the birthday, Florence did celebrate her birthday on the 5th April as shown on the 1939 Register!).
I also have found other more distant relatives who at least prove that my research is correct!
As for my genetic makeup, I don't really think it is that accurate. Apparently I am 29% British, 24% Scandinavian, 23% Irish, 19% Western European, 3% Eastern European, 2% Iberian and have trace elements from Italy/Greece. Yet on all of my branches (the youngest will be no later than 1800) I have nothing but Anglo-Welsh ancestors! I will admit that I have a few illegitimate ancestors but noting that will stretch my results like that! I know us English are a mongrel race, perhaps that is what is being shown in my makeup.